GS/Qt: Add librashader post-processing support

[SternXD]

Description of Changes

• Moved Post-Processing settings out of the Graphics page into its own settings page (Settings > Post-Processing)
• Added optional librashader support for applying .slangp shader presets as post-processing, including a preset picker and runtime parameter controls.

All in-game screenshots below are using the NewPixie CRT slang shader preset.

Settings page

BIOS

NFS MW 2005

Kingdom Hearts

Rationale behind Changes

• I think Post-Processing outgrew its spot on the Graphics page and deserved its own page alongside the other settings categories.
• librashader lets users run RetroArch shader presets (CRT, scanlines, color correction, etc.) on the final image. Kept optional so builds without Rust/cargo aren't affected.

Suggested Testing Steps

• Open Settings > Post-Processing, enable librashader, pick a .slangp preset.
• Test on all renderers
• And make sure the image changes, parameters work, and settings persist after reopening.

Did you use AI to help find, test, or implement this issue or feature?

No.

[SternXD]

rebased and hopefully fixed librashader not working on CMake builds

[Wolf-lbh]

This is fantastic! Is there any chance you would be interested in adding this functionality to Dolphin or PPSSPP? Those are the last of the CRT era systems that have better standalone emulators than RetroArch cores and it would mean the world to me if they had proper shader support. If you didn't try the component video out dock for the PSP you were really missing out.

[chyyran]

Would you be open to upstreaming your patch to spirv-cross2 or allowing me to use your patch, if it is fixing a real bug? spirv-cross2 is not just meant for librashader, there are a couple of other projects that use it as well as ergonomic bindings to SPIRV-Cross in the Rust ecosystem.

[TheLastRar]

Would you be open to upstreaming your patch to spirv-cross2 or allowing me to use your patch, if it is fixing a real bug? spirv-cross2 is not just meant for librashader, there are a couple of other projects that use it as well as ergonomic bindings to SPIRV-Cross in the Rust ecosystem.

I can look at upstreaming it.
The patch fixes long startup time when the VS debugger is attached.
I believe the debugger inspects exceptions to see if it should break, and with the upstream code, a large amount of (caught) exceptions are raised when reflecting larger shaders.
I'm unsure if other debuggers are impacted.

[SternXD]

D3D11 crashing on some shaders pending new librashader release fixed

[chaoticgd]

Reading through the librashader readme, they recommend using librashader_ld.h to load the library at runtime rather than creating a build time dependency on it. I think this would be quite nice since it is quite big, so this way we'd only need to load it if it's actually enabled. Would that be possible?

[SternXD]

Reading through the librashader readme, they recommend using librashader_ld.h to load the library at runtime rather than creating a build time dependency on it. I think this would be quite nice since it is quite big, so this way we'd only need to load it if it's actually enabled. Would that be possible?

Probably. It's not something I really considered at first. If we went that route though, I don't think I'd be able to get it into the 2.8 cycle.

[chaoticgd]

Probably. It's not something I really considered at first. If we went that route though, I don't think I'd be able to get it into the 2.8 cycle.

Okay, so maybe that's an idea for a separate PR then.

[Mrlinkwii]

runs well

[TellowKrinkle]

Probably. It's not something I really considered at first. If we went that route though, I don't think I'd be able to get it into the 2.8 cycle.

Personally I'm not a huge fan of the size of the librashader dependency in general and am trying to make it so we don't need it.